The present invention relates to a coil-driving IC, specifically to a coil-driving IC which is capable of breaking off the connection between an output terminal of the coil-driving IC and a coil by changing the state of the output terminal of the coil-driving IC into a floating state, when the coil is commonly connected to output terminals of a plurality of coil-driving ICs.
A coil can be utilized at a user device for transferring data and/or electric power through a wireless channel. Such a user device may comprise a plurality of coils and a plurality of coil-driving ICs connected to the plurality of coils in order to support various applications installed in the user device. However, a single coil can be shared by all of the plurality coil-driving ICs for use in timely divided manner, by connecting the single coil commonly to the plurality of coil-driving ICs.
For example, in a certain electric device, a first coil-driving IC supporting a function for MST (Magnetic Stripe Transmission) and a second coil-driving IC supporting a function for NFC (Near Field Communication) can be connected commonly to a single coil so that the single coil is utilized by the first coil-driving IC and the second coil-driving IC in a timely divided manner. Such an electric device can be referred to as a ‘coil-sharing electric device’ in this specification. For the coil-sharing electric device, when the coil-sharing electric device is in a first mode that the first coil-driving IC exclusively controls the operation of the single coil, desired circuit performance can be achieved only by breaking off the electric connection between terminals of the second coil-driving IC and the single coil. To the contrary, when the coil-sharing electric device is in a second mode that the second coil-driving IC exclusively controls the operation of the single coil, desired circuit performance can be achieved only by breaking off the electric connection between terminals of the first coil-driving IC and the single coil.
In order to implement such functions, switches can be inserted to connect between each of the coil-driving ICs and the single coil. However, the inserted switches increase the whole price of the coil-sharing electric device.
As another technical approach, a method can be used that a switch is connected at a power source of each of the coil-driving ICs to shut off the power source when necessary. However, because a current leakage path can be formed between the single coil and the internal portion of the shut-off coil-driving IC, undesired effects may occur.